With development of science and technologies, intelligent wearable devices such as a smartwatch are becoming increasingly popular. A smartwatch worn by a user is usually hidden in a sleeve in most time, and the user raises the wrist to view and operate the smartwatch only when needed, for example, reading time.
In other approaches, for an aesthetic purpose, a smartwatch usually keeps a screen lit up after it is powered on. However, a display screen is a high power-consuming component. If the screen is constantly on, a large amount of power is consumed, and a standby time of the smartwatch is greatly shortened.